Air heater



Patented Jan. 2% 1933 UNITED STATES PATENT oFFicr.

CHARLES E. LUCIE, 01 NEW YORK, N. Y., AND PERRY R. CASSIDY, SHORT HILLS, NEW JERSEY, ASSIGNOBS TO THE BABGOCK & WILCOX COMPANY, OF BAYONNE, NEW JERSEY, A. CORPORATION 01' NEW JERSEY mmrna Application fled April 27,

Our present invention relates to the conto rapidly deteriorate in use. This efiect is es ecially noticeable in the late contacted with by the heating fluid be ore its temper ature is reduced by the fluid being heated. It has heretofore been proposed to cover this plate with a layer of refractory material at its high tem erature side, as disclosed in the pending app ication of H. J.'Kerr Serial No. 333,009, filed January 16, 1929. Even when so constructed the plate will receive a substantial amount of heat by conduction through the conduit portions seated therein, which heat may be suflicient to disadvantageously affect the material of the plate.

The eneral object of our present invention is t e provision of a fluid heat exchanger of the character described in which provisions are made for protecting the plate at the heating fluid inlet end of the heat exchanges from heat absorbed directly from the heating fluid and by conduction through the coin duit portions seated therein. A further object of our invention is the provision of special refractory heat insulating members adapted to be received in the seated portions of the heating fluid conduits and characterized b their simplicity of construction, low cost 0 manufacture and ease of installation. Another object is the provision of refractory heat if sulating members for the seated portions of the heating fluid conduits which improves the fluid flow therethrough and thereby the heat transfer between the heating fluid and the fluid to be heated.

. The various features of novelty which characterize our invention are pointed outwith particularity in the claims annexed to and formin a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive 1989. Serial No. 807,778.

matter in which we have illustrated and deicribed preferred embodiments of our invenion.

In the drawing, Fig. l a vertical section through an air heater constructed in accordance with our invention; Fig. 2 is a vertical section on an enlarged scale of a portion of the apparatus illustrated in Fig. 1; Fi 3 is a p an View taken on the line 3-8 of Fig 2; and Fig. 4 is a view similar to Fig. 2 of a modification.

The air heater illustrated in the drawing comprises a casing 1, preferably of rectangular cross-section, forming a part of a flue 2, through which is passed high temperature heating gases from a steam boiler or other apparatus from which high temperature gases are withdrawn. As indicated by the arrows in the drawing, the heating gases pass downwardly to the casin 1 through conduits formed by rows of straight tubes 3 having their opposite end portions expanded into openings 9 formed in tube plates 4 and 5, arranged at the inlet and outlet ends of the tubes, respectively. The air to be heated, such as air used for combustion pur oses, enters through a side inlet 6 in the ower portion of the casing 1, and passes upwardly through the casing sweeping the tubes therein and out through a side outlet 7 arranged adjacent the tube plate 4. A countercurrent flow of the heating fluid and the fluid to be heated is thus provided.

With the heating gas flow described, it is highly desirable that the tube plate 4 be protected from excessive heat imparted thereto by the heating gases contacting with its upper surface and by conduction through the tube portions seated in the plate. As shown in Figs. 2 and 3, the upper end portions 8 of the tubes 3 are considerably enlarged and expanded into the openings 9 in the tube plate, the tube end portions being of greater internal diameter than the main portion of the tubes and projecting beyond the'upper surface of the plate 4. The'enlarged end portions are arranged to receive a layer of heat insulating material preferably in the form of a separate sleeve or thimble,10 havin an in ternal diameter corresponding to the internal the tube seats from the effects of t rature heating gases. The tube plate 4 is erprotected by a layer of refractory heat insulating material 11,-preferably applied to its up r surface in a plastic state after the thim les have been installed. 19 The' ends of the tubes 3 are preferably belled to hold the material 11 in place after it hardens. The up 1 surface of the material 11 is substantially ush with the upper ends of the thimbles 10, and the inlet ends of the 15 thimble passa es are enlarged to facilitate the entrance of the heating gases. With the air heater construction described thetube plate 4 will be adequately protected from the effects oiih' h temperature heating and the duiab' ity of the construction substantially increased. The temperature of thetube plate will be kept closer to the tem perature of its inner face due to the increased resistance to the passage of heat to its outer side effected by the layer of heat insulatin material and the continuous absorption 0 heat by the relatively cold air contacting with its inner side. The described construction is particularly useful in air heaters subject in 3 operation to high temperature heating gases.

In such a construction, by the use of the described protecting arrangement, it is ossible to use a tube'plate of standard materia rather than one of expensive alloy or similar heat resistant material.

In Fig. 4 a construction similar to that of Fig. 2 is illustrated except that the thimbles 10a in Fig. 4 have a passage of Venturi form, the dischar e end of the passage re 'stering 0 with and o substantially the same iameter as the tube internal diameter. The use of refractory sages Increases the velocity of gas flow through the tubes, and avoids the formation of low ressure areas at the inlet and of the tubes w "ch would tend to create eddy currents. At thesame time it permits of thickening the insulating thimble and strengthening it near the end where it has least support by the metal.

While in accordance with the provisions of the statutes we have illustrated and described herein the best forms of our invention now known to us, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of our invention may sometimes be used to advantage without acorresponding use of other features. We claim:

1. In a fluid heat exchanger, 8. flue arranged for the passa of a heatin fluid, a plate 6 member extending a cross sai flue in the path ing'with the outer side of said plate member,

thimbles with Venturi-shaped pas the projecting portions ofsai conduit elements being constructed to hold said material against the outer side of said plate member heat insulatin material positioned in and contactin wit the enlarged end portion of each 0 said conduit elements forming a fluid assa re 'stering with the passage in sai con uit e ement, and means arran ed to provide a flow of a fluid to be heated rough said flue in contact with said con duit elements.

2. In a fluid heat exchanger, a flue arranged for the passage of a heating fluid, a p ate member extending across said flue in the path of saidheatmg fluid and formed with a series of tube ogenings therein, a plurality of tubes in said ue for the ease of said heating fluid and having e argefind rtions seated in the openings in said p ate member and projecting beyond the outer side of said plate member, a layer of heat insulating material surrounding the projectin portions of said tubes and contactin wit 1 the outer side of said plate member, t 0 projecting portions of said tubes being constructed to hold said material a inst the outer side of said plate member, 'mbles of heatinsulating material positioned in and contacting with the enlar d end portions of each of said tubes and aving a passage formed therein registering with the passa in said tubes, and means arran to provi e a flow of a fluid to be heated through said flue in contact with said tubes.

3. In a fluid heat exchanger, 9. flue arran ed no for the passage of a heating fluid, a p ate member extending across said flue in the path of said heating fluid and formed with a series of tube openln therein, a plurality of tubes in said flue or the passa e of said heating fluid and having enlarge and portions seated in the openings in said plate member, a refractory thimble positioned in and contacting with the enlarged end portion of each of said tubes and having an internal cross-sectional area corresponding to the internal cross-sectional area of said tube, and means arran d to provide a flow of a fluid to be heated t rough said flue in contact with said tubes.

4. In a fluid heat exchanger, a flue arranged for the passa e of a heating fluid, a plate member exten 'ng across said flue in the path of said heating fluid and formed with a series of tube openings therein, a plurality of 30 tubes in said flue for the assage of said heating fluid and having en arged end portion) seated in the openings in said plate member and projecting beyond the outer side of said plate member, a layer/of heat insulating material surrounding the projecting portions of said tubes and contacting with the outer side of said plate member, a refractory thimble positioned in and contacting with the enc a flow of a fluid to be heated through- 

